JP2019062626A - Motor drive system - Google Patents

Abstract

To provide a motor drive system capable of improving efficiency without up-sizing a power supply circuit, when driving an open winding structure motor.SOLUTION: A motor drive system includes a motor of an open winding structure including six output terminals where three-phase winding is independent from each other, a primary inverter connected with three output terminals, out of the six output terminals of the motor, and is supplied with a DC voltage converted by an A/D conversion circuit, a secondary inverter connected with three remaining output terminals, out of the six output terminals of the motor, and where one of a positive side power line or a negative side power line is connected commonly with the primary inverter, and a control section for controlling a conduction current and revolution of the motor on the basis of line duty ratios of the primary and secondary inverters in PWM control, and controlling a charging voltage of a capacitor on the basis of a duty ratio common to all phases of the primary and secondary inverters.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a system for driving an open wound motor.

  For example, when driving an AC motor such as a permanent magnet synchronous motor, it is necessary to convert DC power to three-phase AC power using an inverter. However, as the capacity of the motor increases, the current flowing to the inverter also increases, which causes a problem such as heat generation in the power device constituting the inverter.

  In order to solve this problem, in Non-Patent Document 1 and Patent Document 1 etc., the three-phase motor windings are opened without connecting them in a star shape, and inverters are connected to both ends of the three-phase winding to drive. A system has been proposed. According to this system, by using two inverters, the voltage that can be applied to both ends of the three-phase winding can be expanded to about twice, and thus the motor can be driven at higher speed. Alternatively, by increasing the number of turns of the winding, it is possible to drive a motor that outputs high torque with less current.

  The drive system of the open winding motor often takes three forms shown in FIGS. 8 to 10 depending on the circuit configuration. In the configuration shown in FIG. 8, although it is necessary to provide two DC power supplies isolated from each other, the DC voltage of the inverter can be doubled and the zero axis current commonly flowing in the three phase windings does not flow in principle It has the advantage of In the configuration shown in FIG. 9, two inverters share a DC link voltage. Although this configuration requires only one power supply, there is a problem that zero-axis current flows through the DC parts of the inverters of each other. In the configuration shown in FIG. 10, the power supply of one of the inverters is composed of a capacitor, so there may be only one power supply. However, control of reactive power is required to charge the capacitor.

May 2002, The Institute of Electrical Engineers of Japan, D Section Journal Vol. 122, No. 5, p 430-438, "High-efficiency and low-noise motor drive method using an open-winding AC motor and two space voltage vector modulation inverters", Yoshinao Kawabata, Mototoshi Nasu, Takao Kawabata

International Publication No. WO 2016/125557 Brochure

  In the configuration shown in FIG. 8, there is a problem that the circuit for generating two isolated DC power supplies becomes large. Further, in the configuration sharing the DC link shown in FIG. 9, when the application of the third harmonic performed in a general three-phase inverter to improve the voltage utilization rate, currents in the same direction in three phases, That is, there is a problem that the zero axis current flows. Therefore, the voltage utilization rate is limited to 86.6% of the DC voltage. Further, in the configuration shown in FIG. 10, when controlling the reactive power to charge the capacitor on the secondary side, the capacitor charges with a 180 degree phase difference that maximizes the voltage between the primary and secondary inverters. There is a problem that it can not be done and the effective voltage decreases.

  Therefore, a motor drive system is provided that can improve the efficiency without increasing the size of the power supply circuit when driving an open-winding motor.

In the motor drive system of the embodiment, an open-winding motor having three independent three-phase windings and six output terminals,
An AC-DC converter circuit that converts an AC voltage of an AC power supply to DC,
A primary side inverter connected to three of the six output terminals of the motor and supplied with a DC voltage converted by the AC-DC converter circuit;
A secondary side inverter connected to the remaining three output terminals of the output terminal of the motor, wherein one of a positive side power supply line or a negative side power supply line is connected in common to the primary side inverter;
A capacitor connected between the positive side power supply line and the negative side power supply line of the secondary side inverter;
The current and rotation speed to be supplied to the motor are controlled based on the line duty ratio of each of the primary side and secondary side inverters in PWM control, and common to all phases of the primary side and secondary side inverters And a control unit that controls the charging voltage of the capacitor based on the duty ratio of

FIG. 1 shows a circuit configuration of a motor drive system according to a first embodiment. Diagram showing the common mode inductance of an open wound motor Diagram showing an equivalent circuit when two inverters perform simultaneous switching Functional block diagram showing the internal configuration of the secondary side DC voltage control unit Diagrams showing each signal waveform that simulates the operation of the motor drive system It is a second embodiment and is a diagram showing a circuit configuration of a motor drive system. It is 3rd Embodiment and the figure which shows the structure of an air conditioner. A diagram showing a conventional example of a configuration for driving an open winding structure motor (part 1) A diagram showing a conventional example of a configuration for driving an open winding structure motor (part 2) A diagram showing a conventional example of a configuration for driving an open winding structure motor (part 3)

First Embodiment
The first embodiment will be described below with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing a circuit configuration of a motor drive system according to the present embodiment. The motor M is assumed to be a three-phase permanent magnet synchronous motor or an induction machine, but in the present embodiment, a permanent magnet synchronous motor is used. The three-phase windings of the motor M are not connected to each other, and both terminals are in an open state. That is, the motor M includes six winding terminals Ua, Va, Wa, Ub, Vb, and Wb.

  The primary side inverter 1 and the secondary side inverter 2 are each configured by three-phase bridge connection of N-channel MOSFETs 3 which are switching elements. A direct current power supply 4 is connected to the positive side power supply line and the negative side power supply line of the primary side inverter 1. The direct current power supply 4 may be one obtained by converting an alternating current power supply into a direct current. A capacitor 5 is connected to the positive side power supply line and the negative side power supply line of the secondary side inverter 1. The negative power supply line of the primary inverter 1 and the negative power supply line of the secondary inverter 2 are connected in common. The phase output terminals of the inverter 1 are respectively connected to the winding terminals Ua, Va, Wa of the motor M, and the phase output terminals of the inverter 2 are respectively connected to the winding terminals Ub, Vb, Wb of the motor M.

The position sensor 6 is a sensor that detects the rotor rotational position and rotational speed of the motor M, and the current sensor 7 (U, V, W) is a sensor that detects each phase current Iu, Iv, Iw of the motor M . The voltage sensors 8 and 9 detect the voltage V _DC1 of the DC power supply 4 and the voltage V _{DC2 of the} capacitor 5, respectively.

The control device 11 is supplied with the speed command value ω _Ref from the upper control device in the system for driving the motor, and performs control such that the detected motor speed ω matches the speed command value ω _Ref . Control device 11 configures each of FETs 3 forming inverters 1 and 2 based on phase currents Iu, Iv, Iw detected by current sensor 7 and DC voltages V _DC1 and V _DC2 detected by voltage sensors 8 and 9, respectively. Generates a switching signal to be given to the gate of

The current detection / coordinate conversion unit 12 converts the detected currents of the phase currents Iu, Iv, Iw into currents Id, Iq, I0 of axis coordinates of d, q and 0 used for vector control according to equation (1) .

The speed / position detection unit 13 detects the motor speed ω and the rotor rotational position θ from the signal detected by the position sensor 6. The rotational position θ is input to the current detection / coordinate conversion unit 12 and the dq0 / 3 phase conversion unit 17. The speed / position detection unit 13 may be configured to estimate the speed and the position from the voltage / current of the motor M. The speed control unit 14 outputs a q-axis current command I _qRef by, for example, _performing PI operation on the input speed command ω _Ref and the speed ω to calculate the difference between the both. The d-axis current command generation unit 15 generates the d-axis current command value _IdRef for field-weakening control from the DC voltage V _DC1 and the voltage amplitude V _{dq of the} dq axis by, for example, PI calculation of the difference between the two. Do.

The current control unit 16 receives d, q, 0 axis current commands I _dRef , I _qRef , I 0 _Ref , and detected currents Id, I q, I 0 to d, q, 0 axis voltage commands V q, V d, V 0. Output dq0 / 3-phase conversion unit 17, each axis voltage command Vq, a Vd, V0, 3-phase voltage command values of the two inverters 1 and _{2 V u1, V v1, V} w1, V u2, the _{V v2, V w2} (2) Convert by equation.

The secondary DC voltage control unit 18 controls the DC voltage of the secondary inverter 2, that is, the voltage V _{DC2 of the} capacitor 5 to follow the input DC voltage command value V _DC2Ref. The phase voltage command values V _u1 , V _v1 , V _w1 , V _u2 , V _v2 and V _w2 are adjusted, divided by the DC voltage V _DC2 and corrected as described later, and the duties D _u1 'and D of each phase are corrected. Output as _v1 ', D _w1 ', D _u2 ', D _v2 ', D _w2 '. The duties D _u1 ′ to D _w2 ′ are input to the modulation unit 19. The modulation unit 19 applies switching signals, PWM signals U1 ±, V1 ±, W1 ±, U2 ±, V2 ± to be applied to the gates of the FETs 3 constituting the inverters 1 and 2 from the input duties _Du1 ′ to _Dw2 ′. , W2 ± are generated and output.

Next, the operation of the present embodiment will be described with reference to FIGS. 2 to 5. In order to operate the open winding motor M, voltages are applied to the terminals Ua, Va, Wa, Ub, Vb and Wb by the two inverters 1 and 2, respectively. The voltage obtained as a result of the speed control and the current control is divided by the dq0 / 3 phase conversion unit 17 into voltage commands to the inverters 1 and 2 by equation (2). The voltage converted by θ _inv2 = 0 in the equation (2) becomes voltage commands V _u1 , V _v1 and V _w1 to the primary side inverter 1. Then, for example, voltages converted at θ _inv2 = π, which are opposite phases, become voltage commands V _u2 , V _v2 and V _w2 to the secondary side inverter 2. The six voltage command values are converted by the modulator 19 into a total of 12 switching signals for the upper and lower arms. In this way, by applying voltages of opposite phase to the motor M with the two inverters 1 and 2, the voltage amplitude of one equivalent can be increased, and the motor M can be rotated at higher speed.

Here, control of the DC voltage V _DC2 of the secondary side inverter in the present embodiment will be described. As shown in FIG. 2, the common mode component of the 3-phase inductance of the open-winding motor M and L _CM. The inductance L _CM is about several% to 10% of one inductance, although it depends on the motor winding structure.

Considering the timing at which the three phases of inverters 1 and 2 output the same voltage, that is, the equivalent circuit in the case of simultaneous switching, the common mode equivalent circuit shown in FIG. 3 is obtained. When the upper FET 3 of the primary side inverter 1 performs simultaneous switching, a step-down chopper circuit using an inductance L _CM is configured. The lower FET3 secondary side inverter 2 may perform simultaneous switching, constituting the step-up chopper circuit using the inductance L _CM.

Then, the voltage boosted and lowered by these two chopper circuits charges the capacitor 5 of the secondary side inverter 2 and becomes the voltage V _DC2 . Assuming that the upper switching duty of the primary side inverter 1 constituting the step-down chopper in FIG. 3 is D _back , and the switching duty of the secondary side inverter 2 constituting the step-up chopper is D _boost , the voltage V _{DC2 of the} capacitor 5 is 3) It is expressed by a formula.
V _DC2 = V _DC1 D _back / (1-D _boost ) (3)
When D _back = D _boost = 0.5, V _DC2 = V _DC1 , the voltages supplied to inverters 1 and 2 become equal, and as D _back and D _boost increase, secondary side voltage V _DC2 becomes It will be boosted. Thus, the voltage V _DC2 of the capacitor 5 can be controlled by changing the three-phase simultaneous switching amount of the primary side inverter 1 and the three-phase simultaneous switching amount of the secondary side inverter 2.

Next, a control method of the voltage V _DC2 will be described. FIG. 4 shows an internal configuration of the secondary side DC voltage control unit 18. The secondary side DC voltage control unit 18 includes a PI calculation unit 18a, a duty generation unit 18b, an adder 18c, and a subtractor 18d. PI operation unit 18a generates a duty correction value ΔD by _performing PI (Proportional-Integral) operation on the difference between the secondary side voltage command value V _DCRef2 and the secondary side voltage V _DC2 .

The duty generation unit 18 b receives the three-phase voltage command values V _u1 , V _v1 , V _w1 , V _w2 , V _u2 , V _v2 , V of the primary and secondary inverters 1, 2 generated by the dq0 / 3 phase conversion unit 17. Each phase duty command value D _u1 , D _v1 , D _w1 , D _u2 , D _v2 , D _w2 is calculated by dividing _w2 by the respective DC voltages V _DC1 and V _DC2 . Then, the duty correction value ΔD is added to the duty command value of the primary side inverter 1 by the adder 18c to obtain command values D _u1 ', D _v1 ', D _w1 '. As a result, the duty D _{back of the} step-down chopper formed by the common mode inductance L _CM of the primary side inverter 1 shown in FIG. 3 is increased. On the other hand, the duty command values D _u2 , D _v2 and D _w2 of the secondary side inverter 2 are reduced to the command values D _u2 ', D _v2 ' and D _w2 'by subtracting the duty correction value ΔD. As a result, the switching duty of the lower FET 3 of the secondary side inverter 2 is increased. Then, the duty D _{boost of the} step-up chopper shown in FIG. 3 is increased, and the secondary side voltage V _DC2 is boosted.

FIG. 5 shows simulated waveforms in which the open winding motor M is driven in the configuration of the present embodiment and the capacitor voltage V _DC2 on the secondary side is controlled. The primary side voltage V _DC1 is about 280 V, and the voltage command value V _DCRef2 of the secondary side is set to 400 V. Thus, the motor M can also be driven while boosting the voltage V _DC2 . Looking at the U-phase duties _Du1 'and _Du2 ' of the inverters 1 and 2, the amplitude of _{Du 1} 'is larger. This is because although the DC voltage V _DC2 of the inverter 2 is boosted, the DC voltage V _DC1 of the inverter 1 is not boosted. Further, the U-phase duty _Du2 'of the inverter 2 is lowered on average when the DC voltage V _DC2 reaches 400 V by the boost control.

By the operation described above, by boosting the capacitor voltage V _DC2 supplied to the secondary side inverter 2, a higher voltage can be applied by the open winding motor M, and the motor M can be rotated to a higher speed.

As described above, according to the present embodiment, the motor M having an open-winding structure, in which three-phase windings are independent of one another and has six output terminals Ua to Wb, is used as the primary side inverter 1 and the secondary side inverter 2. In the configuration to be driven by this, the DC power supply 4 is connected to the primary side inverter 1 and the capacitor 5 is connected to the secondary side inverter 2. Control device 11 controls the current and rotation speed to be supplied to motor M based on the line-to-line duty ratio of each of inverters 1 and 2 in PWM control, and based on the common duty ratio for all phases of inverters 1 and 2 The voltage V _{DC2 of the} capacitor 5 is controlled. According to this configuration, the secondary side voltage V _DC2 can be boosted and controlled while drivingly controlling the motor M, and the motor M can be rotated to a higher speed.

Specifically, when control device 11 calculates correction value ΔD as a common duty ratio based on the difference between detected value V _DC2 of the voltage of capacitor 5 and input voltage command value V _{DCRef 2} , the first order is calculated. The correction value ΔD is added to the duty ratio of the PWM signal output to the side inverter 1, and the correction value ΔD is subtracted from the duty ratio of the PWM signal output to the secondary side inverter 2. Thus, the secondary side voltage V _DC2 can be boosted and controlled according to the correction value ΔD.

Second Embodiment
Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Only different parts will be described. In the first embodiment, the negative power supply line of the primary inverter 1 and the negative power supply line of the secondary inverter 2 are commonly connected. On the other hand, in the motor drive system of the second embodiment shown in FIG. 6, the positive power supply lines of the inverters 1 and 2 are connected in common. The other configuration is the same as that of the first embodiment.
According to the second embodiment configured as described above, the DC voltage as the reference only changes from the negative side to the positive side, and the same effect as that of the first embodiment can be obtained.

Third Embodiment
FIG. 7 shows the configuration of the air conditioner 30 to which the motor drive system of the present embodiment is applied. The compressor 32 constituting the heat pump system 31 is configured by housing the compression unit 33 and the motor M in the same iron airtight container 35, and the rotor shaft of the motor M is connected to the compression unit 33. The compressor 32, the four-way valve 36, the indoor heat exchanger 37, the pressure reducing device 38, and the outdoor heat exchanger 39 are connected to form a closed loop by a pipe serving as a heat transfer medium channel. The compressor 32 is, for example, a rotary compressor. The air conditioner 30 is configured to have the above-described heat pump system 31.

  At the time of heating, the four-way valve 36 is in the state shown by the solid line, and the high-temperature refrigerant compressed by the compression unit 33 of the compressor 32 is supplied from the four-way valve 36 to the indoor heat exchanger 37 and is condensed. The pressure is reduced at 38 and becomes low temperature and flows to the outdoor heat exchanger 39 where it evaporates and returns to the compressor 32. On the other hand, at the time of cooling, the four-way valve 36 is switched to the state shown by the broken line. For this reason, the high temperature refrigerant compressed by the compression unit 33 of the compressor 32 is supplied from the four-way valve 6 to the outdoor heat exchanger 39 to be condensed, and then decompressed by the decompression device 38 to become a low temperature to be indoors. It flows to the heat exchanger 37 where it evaporates back to the compressor 32. The fans 40 and 41 blow air to the indoor and outdoor heat exchangers 37 and 39, respectively, and the air flow efficiently exchanges heat between the heat exchangers 37 and 39, indoor air, and outdoor air. It is configured to be well done.

By applying the motor drive system of the present embodiment to the air conditioner 30, the motor M is rotated at high speed by boosting the secondary side voltage V _DC2 in the high output operation in which the room temperature is rapidly raised and lowered. On the other hand, in the low output operation in the state where the room temperature has reached the designated temperature, the secondary side voltage V _{DC2 is made} to be the same as the primary side voltage V _DC1 . Thus, the air conditioning operation can be performed with high efficiency.

(Other embodiments)
The current sensor 7 may be disposed for only two phases, and the current of the remaining one phase may be obtained by calculation.
The current sensor 7 may be a shunt resistor or a CT.
The AC power supply may be single phase.
The switching element is not limited to the MOSFET, and other IGBT, power transistor, wide gap semiconductor such as SiC, GaN or the like may be used.
The present invention is not limited to the air conditioner, and may be applied to other products.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  In the drawings, M is an open structure winding motor, 1 is a primary side inverter 1, 2 is a secondary side inverter, 5 is a switch, 11 is a control unit, and 30 is an air conditioner.

Claims (2)

An open-winding motor having three independent three-phase windings and six output terminals;
An AC-DC converter circuit that converts an AC voltage of an AC power supply to DC,
A primary side inverter connected to three of the six output terminals of the motor and supplied with a DC voltage converted by the AC-DC converter circuit;
A secondary side inverter connected to the remaining three output terminals of the output terminal of the motor, wherein one of a positive side power supply line or a negative side power supply line is connected in common to the primary side inverter;
A capacitor connected between the positive side power supply line and the negative side power supply line of the secondary side inverter;
The current and rotation speed to be supplied to the motor are controlled based on the line duty ratio of each of the primary side and secondary side inverters in PWM control, and common to all phases of the primary side and secondary side inverters And a control unit configured to control a charging voltage of the capacitor based on a duty ratio. When the control unit calculates the common duty ratio based on a difference between a detected value of the voltage of the capacitor and a command value of the input voltage,
The common duty ratio is added to the duty ratio of the PWM signal output to the primary side inverter,
The motor drive system according to claim 1, wherein the common duty is subtracted from a duty ratio of a PWM signal output to the secondary side inverter.

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